Analog or digital information may be communicated to a remote receiver using a variety of communication theory techniques. A typical transmission system includes a transmitter, a communication channel, and a receiver. The transmitter converts the analog or digital information into a form that is suitable for transmission over the communication channel. The receiver recreates the original information from the transmitted signal. The communication channel may be any transmission medium such as wire, optical fiber, or merely free space in which the signals are transmitted as an electromagnetic wave (e.g., radio and television signals).
In a typical wireless communication system, a data signal that includes the information is modulated with a carrier signal and transmitted into free space with an antenna. The receiving system has an antenna and receiver that are tuned to the carrier frequency. The receiving system receives and demodulates the transmitted signal and extracts the data signal.
Accurately decoding the data signal at the remote receiver may be dependent on the transmitter and receiver maintaining symbol synchronization during decoding of the information. The receiving system samples the transmitted signal in phase with the transmitter. If the receiver and transmitter were supplied by exactly the same clock source, then the data signal would always be sampled in perfect symbol synchronization with the transmitter. Because this is seldom the case, the transmitter and receiver must be carefully designed such that the receiver can be brought into symbol synchronization with the transmitter.